A home-made nanoporous gold microsensor for lead(II) detection in seawater with high sensitivity and...

A nanoporous gold microelectrode (NPG-μE) was fabricated and used for Pb(II) detection in seawater samples via square wave anodic stripping voltammetry (SWASV). The Au microelectrode (Au-μE) was fabricated by embedding a gold microfiber into a Pasteur pipette, and its surface was further modified by an anodization-electrochemical reduction (A-ECR) method, yielding the NPG-μE. The fabricated electrodes were characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FE-SEM) for electrochemical and structural morphological investigations. SWASV results show a Pb(II) stripping peak at around -0.05 V vs. Ag/AgCl, sat. KCl, which is unusual for common Pb(II) detection (typically occurring at around -0.40 V) in anodic stripping voltammetry (ASV) analysis. The Pb(II) detection at less negative stripping potential is more beneficial. Hence, it exhibited anti-interference properties with Cd(II), which is attributed to the preferential deposition and stripping of the target analyte on the low-indexed crystal planes of the NPG structure. The calibration plot obtained by SWASV was linear in the concentration range of 0.1-10 μM, and the detection limit was found to be 57 nM (correlation coefficient of 0.9974). The NPG microsensor presented a 15-fold enhanced current response compared to Au-μE, with excellent sensitivity (27.2 μA μM^-1 cm^-2). The application of the NPG microsensor was examined by detecting Pb(II) in seawater samples, and a satisfactory performance was obtained.